You don't know about NAT devices then? Here's how to get around it. Apply for a Dynamic DNS at www.dyndns.org. What this does is allows you to alias a dynamic IP address (e.g. 203.x.x.x) to a static hostname (e.g. test.an-example.net). You must update the settings at dyndns.org when your IP changes for this to work. Luckily there are plenty of dyndns clients which automatically updates the settings when your IP changes. Some modems/routers (e.g. Netgear DG-814) have a feature in the settings which allow automatic updates to dyndns.org as well.